Process of working magnesium and high percentage magnesium alloys



Patented Mar. 28, 1933 UNITED STATES PATENT [OFFICE GUSTAV SCHREIBEB, OF BITTERFELD, GERMANY, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO MAGNESIUM DEVELOPMENT CORPORATION, A CORPORATION OF DELAWARE PROCESS 0]? WORKING MAGNESIUM ANDYHIGH PERCENTAGE MAGNESIUM ALLOYS BY ROLLING No Drawing. Application filed December 10, 1931, Serial No. 580,220, and in Germany December 16, 19 80.

The present invention relates to an improved process of working magnesium and high percentage magnesium alloys by rolling. v

It has been observed that in rolling magnesium and high percentage magnesium alloys certain difiiculties appear which do not occur in the rolling of other metals, such as copper, brass, and aluminium. Whereas, with the latter metals it is generally possible to start from east bars (ingots) and to roll them down, in a more or less continuous manner, with considerable reduction in each pass, into plates or thin rods of any convenient gauge, it has been found that, in rolling down cast magnesium. or cast high percentage magnesium alloys, even at the high working temperatures which are always necessary when working these metals, failure of the material soon occurs by splitting or cracking. Hitherto, the only means of preventing such failure-and even that butinadequately-consisted in restricting the reduction in thickness by each pass to a relatively low value, generally with interposed reheating, particularly in the early stages of rollmg. Apparently a process of rolling magnesium and high percentage magnesium alloys, when carried on in this manner, is hardly practicable on an economical basis.

An object of the present invention, therefore, is to obviate the aforementioned difliculties. I have ascertained that the cracking and splitting of the cast material under the stresses exercised by the rolling mill is largely due to the always comparatively coarse-grained structure of the cast material, the coherence of the individual crystals being insuflicient to withstand the high specific stresses of rolling which are concentrated over an extremely narrow portion of the boundary surfaces of the material. It would appear therefrom that it is necessa to improve the grain of the cast material by refining it preliminary to subjecting it to the action of the rolling mill, in order to obviate the drawbacks of the former process.

According to the present invention the refining of the grain of the cast material is effected by subjecting the material, prior torolling, to a plastic deformation at high temperatures by the application of specific pressures which are moderate as compared with those exercised by a rolling mill, and which are further distinguished from the latter by acting on a considerable portion of the boundary surfaces of the material. Such plastic deformation is preferably effected by means of an extrusion press, or by forging, and at the temperatures which are customary in the working of magnesium and high percentage magnesium alloys by these processes.

At the same time, in view of the shaping Emample A cast cylindrical block of 800 mm. length and 170 mm. diameter of an alloy containing approximately 6 percent of aluminium, about 1 percent of zinc, and traces of manganese, the balance being magnesium, is extruded into-a flat rectangular section of 240 mm. x 20 mm. cross-section, at a temperature of about 380 0., which'is the customary temperature of extruding an alloy of that composition. The extruded section, if necessary after reheating, is subjected to rolling in the following manner:

The rolling is carried out in pairs of passes, each pairfollowed by reheating to a temperature slightly higher than that applied to the material prior to the preceding pair of passes, in such a manner that rolling begins at 340 C. and is completed at 380 C. The decrease in thickness is about 10 to 12 percent of the actual thickness in each pass, down to a thickness of the sheets of about 3 mm., and about 5 to 8 percent below 3 mm. thickness down to 1 mm. I

In the manner described the marketable crude products such as thin plate andthe like, canbe turned out without any special difliculty since the pretreated rolling material flows between the rolls in a. far readier and 4 more uniform mannerflthan the cast material.

I claim 1. A process of producing rolled articles from magnesium and high percentage magnesium alloys, which comprises subjecting the metal as cast to a plastic deformation by the application of specific pressures which are moderate as compared with those exer-' cised by a rolling mill, and which act on a considerable portion of the boundary surfaces of the cast metal, and then rolling such deformed metal.

2. A process of producing rolled articles. from magnesium and high percentage magnesium alloys, which comprises subjecting the metal as cast to a plastic deformation by forging, and then rolling such deformed metal.

3. A process of producing rolled articles from magnesium and high percentage magnesium alloys, which comprises subjecting the metal as cast to a plastic deformation by extruding and then rolling such deformed metal.

4. A process of producing rolled articles from magnesium and high percentage magnesium alloys, which comprises subjecting the metal as cast to a plastic deformation by extruding, and then repeatedly subjecting such deformed metal to rolling at temperatures which are successively the higher the thinner the work-piece is rolled out.

5. A process of producing rolled articles .from magnesium and high percenta e magnesium alloys, which comprises su jecting the metal as cast to a plastic deformation by extruding the metal into a section of fiat rectangular shape, and then rolling such deformed metal.

6. A process of producing rolled,sheets from an alloy consisting of about 6 percent of aluminium, about 1 percent of zinc, traces of manganese, the balance substantially being magnesium, which comprises extruding such metal alloy as cast into a section of flat rectangular shape at atemperature of about 380 (3., and then repeatedly subjecting such extruded section to rolling at temperatures successively increasing from about 340 C. to about 380 C.

In testimony whereof, I aflix my si nature.

GUSTAV SGHREI ER.

DISCLAIMER 1,902,905.- Gustav Schretber, Bitterfeld, Germany. PROCESS OF WORKING MAG- NESIUM AND HIGH PERCENTAGE MAGNESIUM ALLOYS BY ROLLING. Patent dated March 28, 1933. Disclaimer filed May 26, 1934, by the assignee, Magnesium Development Corporation, with I .G. F arbenindustrie Aktiengesell:

schaft assenting andjoining. Therefore, enters this disclaimer to certain of the claims of the above identified patent, and x Hereby disclaims claims 3 and 5. Hereby disclaims from the scope of claim 1 any process in which the step of subjecting the metal as cast to a plastic deformation is accomplished by extrusion.-

[Oflicz'al Gazette June 19, 1984.] 

